Abstract

Cr-doped ZnOfilms have been prepared by inductively coupled plasma enhanced physical vapor deposition, and an in-depth study is performed on the chromium doping and oxygen partial pressure dependence of ferromagnetism. The x-ray diffraction and photoluminescence results indicate that the moderate oxygen can relax the lattice strain thus enhancing ferromagnetism which, as confirmed by soft x-ray absorption spectroscopy, is mainly attributed to the Cr valence state transition from to . However, excessive oxygen suppresses the oxygen vacancies and the ferromagnetic exchange. Furthermore, the parabola-like dependence of ferromagnetism on oxygen partial pressure is consistent with the bound magnetic polaron scenario.

Received 15 July 2011Accepted 21 July 2011Published online 05 August 2011

Acknowledgments:

This work was supported by the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 51002176) and the Innovation Program of the Shanghai Institute of Ceramics. The soft x-ray absorption near-edge structure measurements were performed on beam line U19 at the National Synchrotron Radiation Laboratory in University of Science and Technology of China.